1. Field of the Invention
The present invention relates to a railway vehicle brake disc and, further, to a monoblock brake disc having a hub and friction ring connected by a flange.
2. Description of Related Art
Brake discs for trains are typically pressed onto the axle or bolted to the wheel. Axle-mounted brake discs can be made from a single casting or may include a separate hub and friction ring that are bolted together, such as found in U.S. Pat. No. 6,808,050 to Lehmann et al. One-piece or monoblock brake discs typically incorporate radial spokes connecting the hub to the friction ring, such as found in U.S. Pat. No. 4,638,891 to Wirth. Heat generated during braking causes the friction ring to expand radially outward. In the two-piece brake disc design, the friction ring is generally allowed to expand relative to the hub as the disc heats up due to braking. This expansion is accommodated by the disc-hub connection.
Referring to FIGS. 1 and 2, a conventional one-piece brake disc 1 includes a friction ring 2 secured to a hub 3 by a plurality of spaced spokes 4. In this one-piece brake disc design, the spokes 4 that connect the friction ring to the hub 3 are stretched in tension as the friction ring heats up due to braking. The tension of the connecting spokes 4 during braking tends to pull the hub 3 away from the axle, which reduces the press fit of the hub 3 on the axle and can cause the disc to spin on the axle.
Referring to FIGS. 3 and 4, a further conventional design utilizes a brake disc 6 having a flange 7 to attach the friction ring 8 to the hub 9. This brake disc 6 is a two-piece casting with different materials being used for the friction ring 8 than the connecting flange/hub 7, 9, which presents certain problems during manufacturing of the brake disc 6.
United States Patent Application Publication Nos. 2004/0124045 and 2007/0181389 generally disclose brake discs having spokes connecting the hub to the friction ring and are hereby incorporated by reference in their entirety.